The present invention relates to the gripping of material specimens for axial tension and/or compression loading of the specimen in an environmental chamber which has the actuator for the grip on the exterior of the chamber to temperature isolate the actuator from the environment of the grip and specimen.
The measurement of the physical properties of material specimens in high or low temperature environment is a well established requirement in the field of materials testing. An environmental chamber is provided to surround the specimen to be tested in either a high temperature or low temperature atmosphere, for simulating conditions that are required for the testing. These conditions can include vacuum or corrosive gases, as well as heat and cold. Generally, passively activated grips have been used in environmental chambers, but actively actuated grips such as those shown in U.S. Pat. No. 4,537,080 are desirable. Actively actuated grips not only are easy to control through remote hydraulic actuation, but they are convenient for loading and unloading of the specimens, they provide accurate alignment of the specimen in the grip, and the grip can be preloaded to permit tension and compression axial loading of the specimen. The actuators can either be a gas or hydraulic oil. The actuator itself does not operate well within the temperature extremes of an environmental chamber.
Thus, a modular actuator that can be used with several different testing grips and which can be installed through a relatively small port in a wall of an environmental chamber to permit actuation of a grip on the inside of the chamber from an actuator on the outside of the chamber is desirable.
Modular actuators have been advanced, in which the actuators can be taken apart and installed. For example, Instron Corporation has provided in continuous tube coupling between an actuator and a specimen grip so the actuator is spaced from the specimen grip, but it is difficult to install, and has couplings that are larger than the main part of the tube coupling so that passing the connectors through the wall of an environmental chamber is difficult. Installation of such grips requires openings that are larger in size than desirable.